WO2004086794A1

WO2004086794A1 - A random access method of tdd system

Info

Publication number: WO2004086794A1
Application number: PCT/CN2004/000019
Authority: WO
Inventors: Yuehua Chen; Lei Zhou; Sha Ma
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2003-03-26
Filing date: 2004-01-06
Publication date: 2004-10-07

Abstract

The present invention discloses a random access method of TDD system, apply to high-speed data transmission system, this method includes: setting three time duration in each control period, respectively time duration T1, time duration T2 and time duration T3, and setting time duration T2 behind time duration T1, setting time duration T3 behind time duration T2, in high-speed data transmission system, all user terminal of transmitting random access request transmits corresponding uplink synchronization code in time duration T1; network side concentrated transmits the respond of random access request; after user terminal receives the respond, transmits random access information in time duration T3 based on corresponding access information inside. This invention realizes random access by concentrated responding access request of user in a length of time duration, the invention effective utilizes resource of downlink control information, and simple, reliable.

Description

Random access method for time division duplex system TECHNICAL FIELD

The present invention relates to a random access technology in a mobile communication system, and particularly to a method for random access of a user terminal in a time division duplex (TDD) system for high-speed data transmission. Background of the invention

Time division synchronous code division multiple access (TD-SCDMA) system is based on time division duplex (TDD) technology. The system uses different time slots in the same frequency channel to receive and transmit data.

As shown in Figure 1, the physical channel of TD-SCDMA includes a three-layer structure: the first layer is a wireless frame, the second layer is a subframe, and the third layer is a time slot. Specifically, the physical channel is composed of thousands of radio frames, one radio frame is 10 ms, and each radio frame is divided into two consecutive 5 ms subframes. Each subframe includes seven service time slots and three special time frames. Gap.

As shown in FIG. 2, among the seven service time slots, the 0th time slot is fixedly allocated to the downlink, the 1st time slot is fixedly allocated to the uplink, and the remaining time slots can be randomly allocated between the uplink and the downlink. The three special time slots filled with diagonal lines are the downlink pilot time slot (DwPTS), the uplink pilot time slot (UpPTS), and the guard time slot (GP). Among them, the DwPTS time slot is used to send a downlink synchronization code to complete the downlink synchronization; the UpPTS time slot is used to send an uplink synchronization code to complete the initial uplink synchronization. In the TDD system, there are a total of thirty-two downlink synchronization code sequences, and each cell uses one of them. Each downlink synchronization code sequence corresponds to eight different uplink synchronization code sequences (SYNC-UL).

When the user terminal is in an idle state, that is, when there is no service interaction with the base station, the user will maintain downlink synchronization and listen to broadcast information, and learn the corresponding eight SYNC-ULs from the currently used SYNC-DL. Random access refers to a user terminal in a mobile communication system. In the case of dedicated resources, a method of crowding out the public resources of the system in a random manner to transmit certain control information and small data packets to the base station.

As shown in Figure 3, the specific process of random access for user terminals in the current TD-SCDMA system is as follows:

Step 301: The base station sends a DwPTS to the user terminal. After the user terminal obtains the downlink synchronization code, it completes the downlink synchronization according to the downlink synchronization code, and then obtains a usable uplink synchronization code (SYNC-UL) according to the correspondence between the uplink and downlink synchronization codes. ).

Step 302: The user terminal randomly selects an available UpPCH subchannel.

Step 303: Send an uplink synchronization code to the base station through the UpPCH subchannel.

Step 304: After receiving the uplink synchronization code sent by the user terminal, the base station measures the deviation between the first path time of the received UpPCH and the reference time, and estimates adjustment information of the uplink transmission time and transmit power corresponding to the user.

Step 305: The base station notifies the user of the location where the random access information is sent, and the power and time adjustment parameter information through a fast physical access channel (FPACH). Here, the FPACH includes information such as the number of the acknowledged UpPCH, the frame number difference between the subframes in which the current acknowledgement of the UpPCH is detected, the start position of the received UpPCH, and the adjustment of the transmission power of the RACH message.

Step 306: After receiving the FPACH sent by the base station, the user terminal adjusts the transmission power and transmission time of the random access information according to the adjustment parameter information.

Step 307: The user terminal sends a random access message, that is, a RACH message, at the determined position with the adjusted power and timing.

In the above process, the correspondence between the uplink synchronization code sequence and the FPACH, and between the FPACH and the random access channel resources is predetermined, so the location for sending the RACH message is determined.

In order to further improve the access efficiency, the maximum number of transmissions of the UpPCH, the initial transmission power, and the power climbing factor "Pow_Ramp_Step" may be set in advance. In the above process, the first transmission by the user terminal is performed at the initial transmission power.

UpPCH, if the user terminal does not receive a valid response within the expected time, the user terminal increases the signature transmit power with the climb factor Pow_Ramp_Step as the step size, and decreases the signature retransmission counter by 1. If the counter is still greater than 0, it returns to Step 303: Send the uplink synchronization code again; otherwise, report a random access failure to the upper layer. Of course, the number of transmissions cannot exceed the predetermined maximum number of transmissions. The signature mentioned here refers to the uplink synchronization code sequence.

At present, people's requirements for communication systems are getting higher and higher, and they are no longer satisfied with accessing the network through personal computers. Instead, they want to be able to receive data services such as sending emails, performing network browsing, and downloading files at any place. . Therefore, the wireless communication system has evolved from a frequency division multiple access (FDMA) analog communication system to a third generation mobile communication system (3G), and the supported services have gradually evolved from pure voice services to current data and voice mixed services. Until high-speed data services. When transmitting data, the requirements for real-time performance are low, but the requirements for data transmission quality are high. Therefore, in order to ensure the quality of data transmission, more resources must be used for data transmission, and fewer resources are left for control information transmission. Summary of the Invention

In view of this, a system supporting high-speed data transmission based on the TDD system is proposed in another patent application. As shown in FIG. 6, in this system, 128 sub-frames are used as a control period, in which the last eight sub-frames are dedicated Used for centralized transmission of control information. In order to ensure the accurate transmission of control information, an efficient encoding method is used to centrally transmit the control information of the system to reduce the resources occupied by the transmission of control information and optimize the high-speed data transmission system.

Based on the above system design, the present invention provides a random access method for a high-speed data transmission time division duplex system, so that a user terminal can quickly complete random access, and improve the resource utilization rate of the wireless data system.

A random access method of a time division duplex system provided by the present invention is applied to high-speed data In a time-division duplex system for transmission, the method sets a time period T1, a time period T2, and a time period T3 in each control cycle, and the time period T2 is set after the time period T1, and the time period T3 is set after the time period T2. The method further includes:

Α. Each user terminal obtains a downlink synchronization code sent by the network side, and establishes downlink synchronization with the network side;

Β. Obtain all corresponding uplink synchronization codes according to the obtained downlink synchronization code and the corresponding relationship between the downlink synchronization code and the uplink synchronization code. The user terminal randomly selects an available uplink synchronization code, and uses the selected uplink synchronization code within the time period T1. The uplink synchronization code sends a random access request to the network side;

C. After receiving the random access request sent by the user terminal, the network side estimates the access parameters of the corresponding user terminal according to the receiving time and power, and centralizes the estimated access parameter of all access users in the time period T2 Broadcast to all user terminals;

D. After each access user terminal receives all the access parameters, it determines whether it contains its corresponding access parameters according to the uplink synchronization code it uses. If not, the random access fails this time and returns to step B, otherwise Taking out its own corresponding access parameter, and sending random access information to the network side within the time period T3 according to its corresponding access parameter.

The maximum value of the number of random access requests sent by a user terminal is preset; the step B further includes:

The user terminal determines whether the number of random access requests exceeds the maximum. If it exceeds, the random access request fails, and the random access process is ended. Otherwise, within the time period T1, the random access request information is transmitted for the first time by the initial transmission. Power is transmitted to the network side. The method further includes: setting a power climbing factor in advance, and after the first random access fails, the user needs to increase the transmission power by a power climbing factor each time when a random access request is subsequently sent. W The random access request information is a randomly selected uplink pilot channel by the user terminal.

(UpPCH).

The access parameters include location, time adjustment, and power adjustment information for sending a random access channel (RACH) message.

The location parameter of the RACH message is dynamically specified by the network side. Seeking Information.

The method of the present invention is to collectively respond to the random access requests of all users within a period of time to achieve random access of users in a high-speed data transmission TDD system, which has the following advantages and characteristics:

1) The present invention can reduce the occupation of a large amount of downlink resources, and is simple and reliable;

2) The method of the present invention uniformly encodes public control information and sends it collectively within time period T2, which improves the reception performance of public control information and enhances the error correction performance of public control information;

3) The present invention limits the random access request information sent within a control period to the time period T1 before the centralized response information, and limits the position of the random access information subsequently sent by the user to the time immediately after the centralized response information. In the segment T3, it is ensured that the timing adjustment and power adjustment of the random access information sent by the user based on the random access request information sent by the user are effective. Brief description of the drawings

FIG. 1 is a schematic diagram of a physical channel structure in a TD-SCDMA system;

FIG. 2 is a schematic structural diagram of a subframe in a TD-SCDMA system;

FIG. 3 is a schematic diagram of a random access process of a user terminal in an existing TD-SCDMA system; FIG. 4 is a schematic diagram of a control cycle in an optimized high-speed data transmission system; FIG. 5 is a schematic diagram of a process for implementing random access of a user terminal according to the present invention; FIG. 6 is a schematic diagram of a physical layer frame structure of a high-speed data transmission system. Mode of Carrying Out the Invention

The core content of the present invention is as follows: In a high-speed data transmission TDD system, three time periods are set in each control cycle, which are a time period T1, a time period T2, and a time period T3. Send its corresponding uplink synchronization code in the T1 time period; the network side sends a response to the random access request in the time period T2; after receiving the access information, the user terminal sends out the time period T3 in the next control cycle Random access information. Here, the control period may be a time period longer than the frame length, and the settings of the three time periods should ensure that the information responded by the network side is effective for guiding the user to send the access information.

As shown in FIG. 5, the method for implementing the present invention includes the following steps:

Step 501: Each user terminal obtains a downlink synchronization code sent by the network side, and establishes downlink synchronization with the network side.

Step 502: The user terminal obtains all corresponding uplink synchronization codes according to the obtained downlink synchronization code and the corresponding relationship between the downlink synchronization code and the uplink synchronization code, randomly selects an available uplink synchronization code, and uses the selected uplink within the time period T1. The synchronization code sends a random access request to the network side.

Step 503: After receiving the random access request sent by the user terminal, the network side estimates the access parameters of the corresponding user terminal according to the receiving time and power, and centrally estimates the access parameters of all users in the time period T2. Broadcast from all user terminals.

Step 504: After receiving all the access parameters, each access user terminal determines whether it contains its corresponding access parameters according to the uplink synchronization code it uses. If not, the random access fails this time, and returns to step 502. Otherwise, take out the corresponding access parameters. Send random access information to the network side within the time period T3 according to its corresponding access parameter. The following describes the processes of random access in this embodiment from the user side and the network side. The process on the user terminal side is this:

a. Set the signature retransmission counter to M and the signature transmission power to Sig_Init_Pow.

b. After the user terminal obtains the downlink synchronization code, completes downlink synchronization according to the downlink synchronization code, and then obtains a usable uplink synchronization code sequence according to the correspondence between the uplink and downlink synchronization codes, and randomly selects an uplink synchronization code sequence from the sequence.

c. Randomly select one from the UpPCH subchannels available for a given access service level within a few frames before the time period for the centralized transmission of downlink control information.

d. Use the selected UpPCH subchannel to transmit a signature at the signature transmission power, and the signature is the uplink synchronization code sequence; when the signature transmission power exceeds the maximum allowed value, the signature is transmitted at the maximum value.

e. After the signature is transmitted, the FPACH message is detected within the time period immediately after the downlink public control information is transmitted in order to obtain network confirmation. Here, it is necessary to determine whether the FPACH message is returned to the local end to find out the FPACH related to the UpPCH transmitted by the user terminal, which can be obtained by the signature number contained in the FPACH.

If no valid response is detected within the expected time, increase the signature transmit power with the climbing factor Pow_Ramp_Step as the step size and decrement the signature retransmission counter by 1. If the counter is still greater than 0, return to step c. Retransmit within a few frames before the time period in which the control information is collectively transmitted in the subsequent control cycle; otherwise, report a random access failure to the upper layer;

If a valid response is detected within the expected time, the process of setting the time and power level values according to the instructions of the network in FPACH and sending the RACH to the network side at the location indicated by the corresponding FPACH is as follows: After receiving a valid signature, the base station measures the deviation between the first path time and the reference time of the received UpPCH, estimates the adjustment parameters corresponding to the transmission time and power of the user terminal, and immediately follows the subframe in which the UpPCH is received. During the time period for the centralized transmission of downlink control information, a FPACH burst will be sent through the relevant FPACH to confirm the detected signature. Here, the FPACH includes information such as the number of the confirmation signature, the start position of the received UpPCH, the transmission power level of the RACH message, and the transmission position of the RACH message. Since the access request information of all user terminals in a control period is responded within a centralized time, it is not appropriate to specify a criterion for the correspondence between FPACH and PRACH resources in advance. Therefore, the transmission position of the RACH message is Specified by the base station.

It can be seen from the above process that when the number of retransmissions does not exceed the preset maximum value, if the user fails to send an access request, causing the user to fail to correctly receive the response information from the network side, the user can send the access request at a specified position in the next cycle An incoming request, and when the access request is sent next time, the transmit power is increased. Of course, the signature and sending location for the next access request may be different from this time. In addition, the information of the network side responding to the user includes the sending position, time, and power settings of the random access information. These response information can be sent together with other downlink control information.

It should be noted that access requests sent outside the T1 time period in which the access signature is sent are not processed by the above process.

The above description is only the preferred embodiments of the present invention, and is not intended to limit the protection scope of the present invention.

Claims

Claim

1. A random access method for a time division duplex system, which is applied to a high-speed data transmission time division duplex system, characterized in that a transmission period corresponding to a fixed number of subframes is set as a control period in the system, The time period T1, the time period T2, and the time period T3 are set within each control period, and the time period T2 is set after the time period T1, and the time period T3 is set after the time period T2. The method further includes the following steps:

A. Each user terminal obtains the downlink synchronization code sent by the network side, and establishes downlink synchronization with the network side. To obtain all the corresponding uplink synchronization codes, the user terminal randomly selects an available uplink synchronization code, and uses the selected uplink time period within the time period T1. The uplink synchronization code to send a random access request to the network;

C. After the network side receives the random access request sent by the user terminal, it estimates the access parameters of the corresponding user terminal according to the reception time and power, and centralizes the estimated access parameters of all user terminals in the time period T2. All user terminals broadcast;

D. After each access user terminal receives all the access parameters, it determines whether it contains its corresponding access parameters according to the uplink synchronization code used by it. If not, the random access fails this time and returns to step B, otherwise To obtain the corresponding access parameter of itself; according to the corresponding access parameter of itself, send random access information to the network side within time period T3.

2. The method according to claim 1, wherein a maximum value of the number of random access requests sent by a user terminal is set in advance; the step B further comprises:

The user terminal determines whether the number of random access requests has exceeded the maximum. If it exceeds, the random access request fails, and the random access process is ended. Otherwise, information is requested at the next control cycle.

3. The method according to claim 1, wherein the random access request letter For the first time, the message is transmitted to the network side with the initial transmission power.

4. The method according to claim 1 or 3, further comprising: setting a power climbing factor in advance, and after the first random access fails, the user sends a random access request every time after The transmit power needs to be increased by a power climb factor.

5. The method according to claim 1, wherein the random access request information is transmitted by a user terminal through a randomly selected uplink pilot channel (UpPCH).

6. The method according to claim 1, wherein the access parameters include location, time adjustment, and power adjustment information for sending a random access channel (RACH) message.

7. The method according to claim 6, wherein the location parameter of the RACH message is dynamically specified by the network side.

8. The method according to claim 2, wherein the user terminal sends random access request information to the network side by using an randomly selected uplink synchronization code each time.

9. The method according to claim 2, wherein the user terminal resends the uplink synchronization code to the network side on the randomly selected uplink synchronization channel each time.

10. The method according to claim 1, wherein the control period is a time period longer than a frame length.